A rehabilitation program after anterior cruciate ligament reconstruction is of great importance to obtain a satisfactory prognosis after surgery. However, there is still an onging debate over whether closed kinetic chain or open kinetic chain exercises should be chosen. Our study was designed to compare the in vivo tibiofemoral kinematics during closed kinetic chain and open kinetic chain exercises. Eighteen healthy volunteers were asked to perform box squat and unloaded/10 kg-loaded seated knee extension. In vivo 3-dimensional analysis of tibiofemoral kinematics of different motions were determined using a dual fluoroscopic imaging system. The study found significantly more tibial anterior displacement during loaded seated knee extension than during unloaded seated knee extension from 25°-50° of knee flexion (p ≤ 0.031). The knees exhibited significantly more internal tibial rotation and lateral tibial translation during the box squat than both seated knee extensions during mid-flexion. In addition, the knees showed less internal-external (IE) range of motion (ROM) from 20°- 75° of flexion (p < 0.001) and medial-lateral (ML) ROM from 75° to full extension (p ≤ 0.006) during box squat than both extensions. This knowledge may help optimize rehabilitation plans for patients post ACL reconstruction.

Background: The glenoid track concept has been widely used to assess the risk of instability due to bipolar bone loss. The glenoid track width was commonly used as 83% of the glenoid width to determine if a lesion was on-track or off-track. However, the value was obtained under static conditions, and it may not be able to reflect the actual mechanism of traumatic dislocation during motion. Purpose: To compare the glenoid track width under dynamic and static conditions using a dual-fluoroscopic imaging system. Study Design: Controlled laboratory study. Methods: In total, 40 shoulders of 20 healthy volunteers were examined for both dynamic and static tests within a dual-fluoroscopic imaging system at 5 different arm positions: 30°, 60°, 90°, 120°, and 150° of abduction, keeping the shoulder at 90° of external rotation. The participants performed a fast horizontal arm backswing for dynamic tests while keeping their arm in maximum horizontal extension for static tests. Computed tomography scans were used to create 3-dimensional models of the humerus and scapula for 2-dimensional to 3-dimensional image registration. Magnetic resonance imaging scans were obtained to delineate the medial margin of the rotator cuff insertion. The glenoid track width was measured as the distance from the anterior rim of the glenoid to the medial margin of the rotator cuff insertion and compared between static and dynamic conditions. Results: The mean glenoid track widths at 30°, 60°, 90°, 120°, and 150° of abduction were significantly smaller under dynamic conditions (88%, 81%, 72%, 69%, and 68% of the glenoid width) than those under static conditions (101%, 92%, 84%, 78%, and 77% of the glenoid width) (all P < .001). The glenoid track width significantly decreased with the increasing abduction angles in the range of 30° to 120° under static conditions (all P < .003) and 30° to 90° under dynamic conditions (all P < .001). Conclusion: A smaller dynamic-based value should be considered for the glenoid track width when distinguishing on-track/off-track lesions. Clinical evidence is needed to establish the superiority of the dynamic-based value over the static-based value as an indicator for augmentation procedures. Clinical Relevance: Some off-track lesions might be misclassified as on-track lesions when the original commonly used static-based value of 83% is used as the glenoid track width.

The kinematics of the cervical spine during various functional neck motions has been widely reported. However, no data has been reported on the cervical intervertebral kinematics during walking, the most frequently performed daily functional activity. In this study, we evaluated cervical kinematics and disc deformation of asymptomatic subjects during a gait cycle using a dual fluoroscopic imaging system. Our measurements showed that the vertical translation of the cervical spine (1.6 ± 0.1 Hz) occurred at twice the frequency of the gait cycle (0.8 ± 0.1 Hz). The overall ranges of motion (ROMs) of the entire (C2-T1) cervical spine were 5.0 ± 3.1° in the flexion-extension rotation, 3.4 ± 1.0° in the lateral-bending rotation, and 5.8 ± 2.1° in the axial-twisting rotation during walking. Each intervertebral disc (measured at the disc centre location) dynamically deformed in its axial direction in a range of 16.2 ± 5.7% ~ 23.7 ± 8.7% (without significant differences among different segment levels, p > 0.05), similar to the ranges of shear deformations of the same disc (p > 0.05, except for the C7-T1 disc, where p = 0.010). These data could be useful for improvements of diagnosis and treatment methods of cervical pathologies.

Background: Arthroscopic repair with the biceps rerouting (BR) technique has been determined to lead to promising clinical and biomechanical outcomes for treating large-to-massive rotator cuff tears (LMRCTs). However, the in vivo effects of BR on glenohumeral kinematics during functional shoulder movements have not been fully elucidated. Purpose: To investigate whether BR provides a better restoration of shoulder kinematics compared with conventional rotator cuff repair (RCR). Study Design: Controlled laboratory study. Methods: Patients who underwent either repair with the BR technique (BR group) or RCR alone (RCR group) for treating LMRCTs between January 2021 and May 2022 were enrolled. They underwent a 1-year postoperative kinematic evaluation of bilateral shoulders by performing scapular-plane abduction with a dual fluoroscopic imaging system. Glenohumeral translation in the superior-inferior (S-I) and anterior-posterior (A-P) directions was assessed in shoulder abduction at 10° increments. Moreover, the mean, maximum, minimum, and range of glenohumeral translation were calculated throughout the entire movement. Results: A total of 9 patients were enrolled in each group for final analysis, and baseline characteristics were comparable between the groups. In the RCR group, compared with contralateral shoulders, the operative shoulders showed increased superior humeral head translation during lower abduction angles of 30° to 50° (all P ≤ .004), with a greater maximum ( P = .014) and a larger range ( P = .002) for S-I translation throughout the entire movement. In the BR group, no significant differences between operative and contralateral shoulders were detected in any kinematic variables for S-I translation (all P ≥ .132); however, the operative shoulders exhibited a larger maximum ( P = .031), a smaller minimum ( P = .008), and a larger range ( P < .001) for A-P translation throughout the entire movement compared with the contralateral shoulders. Conclusion: BR successfully reduced residual superior humeral head translation compared with conventional RCR and restored normal S-I glenohumeral kinematics in the treatment of LMRCTs. However, A-P glenohumeral kinematics was not fully restored after BR, and its effect on long-term clinical outcomes requires further investigation. Clinical Relevance: BR can be a promising technique to treat LMRCTs. However, its potential adverse effects on A-P glenohumeral kinematics should not be ignored, requiring further clinical evidence to determine long-term outcomes.